JP2672087B2 - Fuel injection control device for diesel engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for a diesel engine, and more particularly to an improved control device for stabilizing idle rotation. (Prior Art) The idle rotation speed of a diesel engine is easily affected by the operating environment, and varies greatly depending on the temperature of engine cooling water and oil, intake air temperature, fuel properties, and other factors that change with time. On the other hand, for example, JP-A-56-101059 and 57,
As can be seen in Japanese Patent Laid-Open No. 105550, etc., an electronic control system for a fuel injection pump is known, which allows stable idle operation. That is, the fuel injection pump used in this type of control device is provided with a drive means, such as a pulse motor, as a mechanism for adjusting the fuel injection amount, and the fuel injection amount is based on an electrical control signal. Since it is possible to precisely control the engine speed, it is possible to easily realize automatic control of idle rotation, which is difficult with mechanically controlled injection pumps.Specifically, the deviation of the idle speed from the target value is fed back. By adjusting the fuel injection amount, the idle rotation speed can always be kept constant regardless of the fluctuation of the operating environment. (Problems to be Solved by the Invention) However, in such a conventional injection control device, the fuel injection amount at the time of idle operation is predetermined, and each time the idle rotation speed deviates from the target value, Since the rotation was kept constant by correcting the shortage or excess of the fuel injection amount, the responsiveness was insufficient. In other words, although stability is certainly exhibited during steady idle operation, once the vehicle is separated from the idle state, it will be corrected again from the initial idle fuel injection amount when the accelerator is returned. Could be delayed, and there was a risk of undershoot, hunting, or even stall during idle rotation. The present invention has an object to solve such conventional problems. (Means for Solving the Problems) In order to achieve the above object, the present invention includes a fuel injection pump whose fuel injection amount is variably controlled based on an electric control signal, as shown in FIG. Diesel engine 101
At the rotational speed detection means 10 for detecting the engine rotational speed
2 and idle detection means 103 for detecting the idle operation state
Further, in cooperation with the respective detecting means, the correction amount ΔQ with respect to the basic fuel injection amount Q is increased / decreased in the direction in which the difference between the actual engine speed and the target value at the time of idling operation is decreased to feedback control the supplied fuel amount. The control means 104 and the basic fuel injection amount Q are increased when the correction amount ΔQ exceeds a predetermined value in the fuel injection amount increasing direction, and are decreased when the correction amount ΔQ exceeds the predetermined value in the fuel decreasing direction. Therefore, the injection amount setting means 105 for learning-correcting the basic fuel injection amount Q is provided so that the correction amount ΔQ is always within a predetermined value. (Operation) Based on the above configuration, the control unit 104 always performs the idle rotation control by increasing or decreasing the correction amount ΔQ with the corrected basic injection amount Q via the injection amount setting unit 105 as an initial value, and the correction. The basic fuel injection amount Q itself is learned and corrected so that the amount ΔQ falls within a predetermined value. Therefore, the idle speed is quickly controlled to the target speed in response to the engine speed fluctuation factors such as the magnitude of friction of the engine and changes over time, and even when the engine is returned to the idle operation from the load There is no risk of a decrease or stall of the engine, and conversely, a smooth drivability or acceleration is exhibited even when shifting from idle operation to load operation without a decrease in torque. (Example) Hereinafter, an example of the present invention is described based on an accompanying drawing. FIG. 2 is a flow chart showing the mechanical construction of the embodiment of the present invention, and FIG. 3 is a flow chart showing the operation contents of the control system. In FIG. 2, 1 is an air cleaner, 2 is an intake pipe, 3
Is a main combustion chamber, 4 is a swirl chamber, 5 is a glow plug, 6 is an injection nozzle, 7 is a fuel injection pump, 8 is an exhaust pipe, 9 is an intake throttle valve, and 10 is a negative pressure drive for opening and closing the throttle valve 9. apparatus,
Reference numeral 11 is an EGR control valve for controlling the exhaust gas recirculation amount, 12 is a second negative pressure drive device for driving the EGR control valve 11 to open and close, and 13A and B are negative pressures supplied to the negative pressure drive devices 11, 12. An electromagnetic valve for controlling the duty ratio, 14 is a vacuum pump serving as a supply source of the negative pressure, and 15 is a constant pressure valve for making the negative pressure generated by the vacuum pump 14 constant. The fuel injection pump 7 is a well-known distribution type injection pump configured to control the fuel injection amount based on an electric signal, for example, a servo motor for driving a load control lever or a control sleeve thereof. It is different from the mechanical control type in that a lever position control signal OC ₄ is given to a (not shown) via the servo circuit 18 and the fuel injection amount is variably controlled accordingly. Reference numeral 16 is a battery, 17 is a glow relay that controls energization to the glow plug 5, 18 is a servo circuit that controls the fuel injection amount of the injection pump 7 as described above, and 19 is a glow lamp that indicates the energization state of the glow plug 5. Is. 20 is an accelerator position sensor that outputs an accelerator position signal IS ₁ corresponding to the depression angle of the accelerator pedal, and 21 is a reference pulse IS _{2 for} each crank angle reference position (for example, 120 degrees).
Is a rotation sensor that outputs a unit pulse IS ₃ for each unit angle (for example, 1 degree), and 22 is a neutral switch that detects that the transmission is in the neutral position and outputs a neutral signal IS ₄ . In addition to this, although not shown, a clutch switch for outputting a signal according to the on / off state of the clutch is provided, and the accelerator position sensor 20 and the neutral switch 22 are provided with the clutch switch 10 shown in FIG.
3, and the rotation sensor 21 also corresponds to the rotation speed detecting means 102. 23 is a vehicle speed sensor that outputs a vehicle speed signal IS ₅ according to the traveling speed of the vehicle, 24 is a temperature sensor that outputs a temperature signal IS ₆ according to the engine cooling water temperature, and 25 is each time the injection nozzle 6 starts fuel injection. Lift sensor that outputs injection start signal IS ₇ , 2
An atmospheric density sensor 6 outputs an atmospheric density signal IS ₈ according to the temperature and pressure of the atmosphere. Further, 27 is a control device that outputs a predetermined control signal based on the above various signals to control the EGR rate and the fuel injection amount, and is configured as a microcomputer that comprises the CPU 28, ROM 20, RAM 30, I / O interface 31, etc. The functions of the control means 104 and the idle injection amount setting means 105 of FIG. 1 are included. This control device 27 controls the throttle valve opening control signal OS ₁ and the EGR control signal OS, which are pulse signals to the solenoid valves 13A and 13B, respectively.
₂ is output and the duty ratios of these pulse signals are changed to change the effective opening amounts of the solenoid valves 13A and 13B to continuously and variably control the opening amounts of the intake throttle valve 9 and the EGR control valve 11. The duty ratio is stored in advance in the ROM 29 in the form of a table, and the command value of the duty ratio is obtained by table lookup from the accelerator pedal depression angle (IS ₁ ) and the engine speed (IS ₂ or IS ₃ ) and is required for this. It is output to the solenoid valves 13A and 13B after being corrected according to the water temperature and atmospheric density. On the other hand, the fuel injection amount control is basically the same as the above, and the table of command values (lever position control signal OS ₄ ) formed in the ROM 29 as shown in FIG. 4 is set to the engine operating state. It is read accordingly and is applied to the servo circuit 18 to control the fuel injection amount of the fuel injection pump 7. in this case,
The lever position signal IS ₉ indicating the actual lever position is fed back from the fuel injection pump 7 to the servo circuit 18 for accurate injection amount control. In addition to the above, the control device 27 uses a fuel cut signal for shutting off the fuel supply to the fuel injection pump 7 when the engine is stopped.
Outputs OS ₃ , injection timing control signal OS ₅ for controlling fuel injection timing, glow control signal OS ₆ for controlling opening / closing of the glow relay 17 during warm-up operation, monitor signal OS ₇ for driving the lamp 19 during glow operation, etc. . The above is the same as the well-known electronically controlled fuel injection device for diesel engine, but in the present invention, as already described, the fuel injection amount necessary to secure the predetermined idle rotation speed is always corrected. Set the fuel injection amount. However, in this case, since the fuel injection amount is represented by the lever position of the fuel injection pump 7, the lever position signal IS ₉ indicating the actual position thereof is controlled by the offset amount ΔS (voltage decrease value) from the predetermined initial value. The injection lever amount is given to change the apparent lever position with respect to the control device 27, and the injection amount is determined by using the result of the increase / decrease correction of the offset amount ΔS as a new initial value of the lever position. Next, details of the control operation example of such idle rotation control will be described with reference to FIG. In this control, first, the engine speed Ne calculated based on the signal IS ₂ or IS ₃ from the rotation sensor 21 is compared with a predetermined reference value N ₀ to determine whether or not it is in a stopped state (step 30
1). When Ne <N ₀ , the engine is in a stopped state. At this time, if the offset amount ΔS or the fuel injection amount Q is corrected, Ne will rise due to excess fuel after starting. Therefore, the correction process of ΔS is bypassed and the step is skipped. Proceed to the processing of 310 and below. On the other hand, when Ne ≧ N ₀ , it is considered that the engine is in operation, and it is then determined whether or not the engine is in the idle operation state (step 302). This is the accelerator position sensor 20, the neutral switch 22, the clutch. Depending on the switch state, for example, when the accelerator is off, the transmission is in neutral, and the clutch is engaged, it is determined that the transmission is idle. If not idle,
The correction process of S is bypassed, and the process proceeds to step 310 and subsequent steps. If the engine is in the idle state, then the current correction value ΔQ of the idle injection Q is compared with predetermined lower limit value A and upper limit value B (step 303). At this time, if A <ΔQ <B, this indicates that the idle speed has already been limited within the allowable range around the target value as a result of the injection amount correction described later, so the correction process of ΔS is performed. Detour and proceed to step 310. On the other hand, when ΔQ ≦ A, this means that the offset amount ΔS, which is the subtraction value from the lever initial position, is too small,
In other words, since the idle injection amount Q is too large and Ne is larger than the target idle rotation, the process proceeds to step 304 and subsequent steps for increasing ΔS. In this processing, considering the stability of control, first, the interval time T is integrated by a timer, and when this becomes a predetermined value t or more, T is reset and then ΔS is increased by a predetermined amount (steps 304 to 306). ). On the other hand, if ΔQ ≧ B in the determination of step 303, this is because ΔS is too large and Q is too small so that stall and hunting are likely to occur. Is reduced (steps 307 to 309). Next, the ΔS corrected in this way is subtracted from the current lever position signal IS ₉ to newly set it IS _9, and based on this and the rotation speed Ne, the table formed as shown in FIG. Read out the fuel injection amount Q. The Q recorded in the table is actually the basic value of the lever position control signal, and the sum of this and the current idle fuel injection amount ΔQ is used as OS ₄
Is output to the fuel injection pump 7 (steps 310 to 31).
2). Finally, Ne after the above injection amount correction is detected, and it is determined whether or not this matches the target value Ni of the idle rotation speed,
If Ne = Ni, one control cycle is terminated and the process returns to the first one. If Ne <Ni, ΔQ is increased by a predetermined amount, and if Ne> Ni, it is similarly decreased and the process returns to the first process (steps 313 to 315). To summarize the above processing, if the idle speed deviates from the target value due to changes in temperature, water temperature, etc. during the process of repeated control, the apparent lever position changes to compensate for this. Accordingly, the controller 27 corrects ΔQ in the direction in which the rotation speed changes toward the target value.
As a result, when the idle rotation speed matches the target value, ΔQ at that time is kept constant unless the idle rotation speed changes again due to the above factors. In other words,
Once the idling speed that meets the target value is obtained, the proper value of the idle fuel injection amount is stored, so even if the required load (lever position) fluctuates and then returns to the idling state, an appropriate amount of idling is immediately returned. Fuel is injected. For this reason, an extremely stable idle rotation state can be obtained without causing stall or undershoot. In addition, since the basic injection amount Q is corrected so that ΔQ always stays within a certain small value in this way, there is little torque change when exiting from the idle operation state due to an increase in load demand, and a smooth drivability. Or acceleration can be obtained. Further, according to the above processing, the correction amount ΔQ is fed back to correct the offset amount of the lever position. Therefore, even if there is a mounting error in the sensor or the like for detecting the lever position, the output value caused by the mounting error. The advantage is that the deviation of is corrected automatically. (Effects of the Invention) As described above, according to the present invention, fuel, intake air, cooling water,
By adjusting the basic fuel injection amount itself in response to the engine oil temperature and other factors that change the idle speed, the correction amount for the basic injection amount is always within the specified range. The control response to the idle rotation speed and the accuracy can be improved. That is, in the present invention, since the basic fuel injection amount and the correction amount are separately calculated, it is possible to promptly inject an appropriate fuel based on the basic fuel injection amount even when the vehicle is returned to the idle operation state after traveling. While undershoot, hunting, stall, etc. due to control response delay can be reliably avoided, the drivability at the time of accelerating from the idle operation state is also improved. Further, according to the present invention, it is possible to obtain the effect that the required output can be accurately exhibited by increasing the amount of fuel corresponding to the required output based on the basic fuel injection amount as a reference even in an operating state other than idle. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram corresponding to the claims of the present invention. FIG. 2 is a mechanical block diagram of an embodiment of the present invention, FIG. 3 is a flow chart showing the operation contents of a control system relating to idle speed control, and FIG. 4 shows the contents of a table of fuel injection amounts used in the control. It is a control characteristic diagram. 6 ... Injection nozzle, 7 ... Fuel injection pump, 18 ... Servo circuit, 20 ... Accelerator position sensor, 21 ... Rotation sensor, 22 ... Neutral switch, 23 ... Vehicle speed switch, 27 ... Control device.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Atsunori Hashimoto               2 Takaracho, Kanagawa-ku, Yokohama-shi Nissan Motor               Inside the corporation (72) Inventor Shinichiro Okayama               2 Takaracho, Kanagawa-ku, Yokohama-shi Nissan Motor               Inside the corporation (72) Inventor Masato Nagasago               2 Takaracho, Kanagawa-ku, Yokohama-shi Nissan Motor               Inside the corporation                (56) References JP-A-57-38628 (JP, A)

Claims (1)

(57) [Claims] In a diesel engine equipped with a fuel injection pump whose fuel injection amount is variably controlled based on an electric control signal, a rotation speed detection means for detecting an engine rotation speed, an idle detection means for detecting an idle operation state, and A control unit that cooperates with each detection unit to perform feedback control of the supplied fuel amount by increasing or decreasing the correction amount ΔQ with respect to the basic fuel injection amount Q in the direction in which the difference between the actual engine rotation speed during idle operation and the target value decreases. , The basic fuel injection amount Q is increased when the correction amount ΔQ exceeds a predetermined value in the fuel injection amount increasing direction, and is decreased when the correction amount ΔQ exceeds the predetermined value in the fuel decreasing direction. A fuel injection control device for a diesel engine, comprising: an injection amount setting means for learning and correcting the basic fuel injection amount Q so that ΔQ is always within a predetermined value.